In four-jet events from e+e- --> Z0 --> multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle theta-NR* and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor N(C) to the fermionic Casimir operator C(F): N(C)/C(F) = 2.55 +/- 0.55(stat.) +/- 0.4(fragm. + models) +/- 0.2(error in bias) in agreement with the value 2.25 expected in QCD from N(C) = 3 and C(F) = 4/3.
Experimental-study of the Triple-gluon Vertex
GASPARINI, UGO;MARGONI, MARTINO;RONCHESE, PAOLO;SIMONETTO, FRANCO;ZUMERLE, GIANNI;
1991
Abstract
In four-jet events from e+e- --> Z0 --> multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle theta-NR* and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor N(C) to the fermionic Casimir operator C(F): N(C)/C(F) = 2.55 +/- 0.55(stat.) +/- 0.4(fragm. + models) +/- 0.2(error in bias) in agreement with the value 2.25 expected in QCD from N(C) = 3 and C(F) = 4/3.Pubblicazioni consigliate
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